1. Field of the Invention
This invention relates to an image forming apparatus such as a copier or a printer, and particularly to an image forming apparatus for forming a layered image like a color image on a recording material by the utilization of a plurality of image forming stations and a unit detachably mountable on such apparatus.
2. Related Background Art
Reference is had to FIG. 5 of the accompanying drawings to describe an example of the construction of an image forming apparatus of the electrophotographic type for obtaining multicolored images, i.e., a so-called color image forming apparatus.
The color image forming apparatus shown in FIG. 5 is a color image forming apparatus of the so-called four-drum type, and a rotary transferring member, i.e., an intermediate transferring belt 6 in the present example, is passed over a driving roller 7 and a driven roller 8, and is rotated in the direction of arrow. Color image forming stations Y, M, C and Bk for yellow, magenta, cyan and black, respectively, are provided along the direction of movement of the intermediate transferring belt 6, and accordingly, four photosensitive drums 1 (1a to 1d) which are image bearing members are disposed in succession on the upper side of the moving intermediate transferring belt 6.
Around the photosensitive drums 1 (1a to 1d), there are installed image forming means such as charging means 2 (2a to 2d), laser scanners 3 (3a to 3d) as exposing means, and developing means 4 (4a to 4d) provided with developing rollers and containing developers (toners) of the respective colors therein. The image forming means of the respective colors are similar in construction to one another with the exception that Y, M, C and Bk toners are contained in the developing containers of the developing means 4a to 4d. Also, the photosensitive drum 1, the charging means 2 and the developing means 4 are made into a unit (cartridge) which is detachably mountable on the main body of the apparatus.
Toner images of the respective colors developed on the respective drums 1a to 1d by the developing means 4a to 4d are successively transferred onto the intermediate transferring belt 6 by the use of transferring means 5 (5a to 5d), and a full color image is obtained by the toners of four colors, i.e., yellow, magenta, cyan and black.
In the color image forming apparatus in the present example, no cleaning mechanisms are disposed around the photosensitive drums 1a to 1d, and this is because this apparatus adopts a cleaner system for collecting untransferred toners by the developing means 4a to 4d simultaneously with developing, and thereby, the downsizing and reduced cost of the apparatus become possible and further, it becomes possible to extend the life of the photosensitive drums because no cleaning blades frictionally contact with the photosensitive drums.
Description will now be made of the image forming operation of the color image forming apparatus constructed as described above.
A laser beam modulated in conformity with image data from a host apparatus such as a personal computer is applied by the exposing means 3a to 3d to the surfaces of the photosensitive drums 1a to 1d uniformly charged by charging rollers which are the charging means 2a to 2d, whereby desired electrostatic latent images are formed for the respective colors. These latent images are reversal-developed and visualized as toner images in developing regions by the developing means 4a to 4d which are developing apparatuses disposed in opposed relationship with the photosensitive drums 1a to 1d and containing the toners of the respective colors therein. These toner images are successively transferred to the intermediate transferring belt 6, and are further transferred to a recording medium P fed by sheet feeding means (not shown) and conveyed by conveying means. These color toner images are melted and fixed by a fixing apparatus (not shown), and are permanently fixed on the recording medium P, whereby a desired color print image is obtained.
In the color image forming apparatus shown in FIG. 5, the photosensitive drums 1a to 1d, charging means 2a to 2d and developing means 4a to 4d which are the image forming means are made integral with one another to assume the form of process cartridges 10a to 10d as shown in FIG. 6 of the accompanying drawings. The process cartridges 10a to 10d are made detachably mountable on the main body of the apparatus by cartridge mounting means (not shown).
In the color image forming apparatus of the above-described construction, provision is made of means for detecting the amount of remaining toner in each of the cartridges 10a to 10d, and when the toner in a cartridge of a certain color has become null and that cartridge has come to the end of its life, it is made possible to continuedly use the apparatus by a user simply interchanging that cartridge, and the maintenance by a serviceman as done in a copier or the like becomes unnecessary.
Also, for example, the photosensitive drums 1a to 1d, charging means 2a to 2d and developing means 4a to 4d which are image forming means are made integral with one another to form cartridges, whereby there is born the merit that stable and good images free of inconvenience can always be obtained until the end of the life of the cartridges and moreover, the user can easily effect the interchange of any cartridge when it has come to the end of its life.
However, in the color image forming apparatus of the construction as described above, image formation using four colors is not always effected, but image formation of single black color is effected in the case of black-and-white images and besides, image formation by various modes such as a two-color mode using only yellow and magenta, and a three-color mode using yellow, magenta and cyan is effected.
That is, there are a four-color mode using four colors, a three-color mode using only three colors of four colors, a two-color mode using only any two colors of four colors, and a single color mode using any one of four colors.
Here, the single color mode will be described as an example. Usually, image formation (printing) is effected in a full color mode (four-color mode), and a speed difference is given between the photosensitive drums and the intermediate transferring belt to thereby secure a good transferring property and obtain a good image.
Next, when for example, a monochromatic image of a single black color is to be formed, the other image forming means than for black are not operated, and a similar image forming operation is performed with the intermediate transferring belt 6 and the photosensitive drums 1a to 1c spaced apart from one another by a mechanism, not shown. In this case, however, the construction of the apparatus becomes complicated and the cost thereof becomes very high or the apparatus becomes bulky.
So, in the case of the single black mode, it is practised that the intermediate transferring belt 6 is not spaced apart and the photosensitive drums 1a, 1b and 1c of the other colors continue to be rotated. In this case, there is not the problem of the increased cost of the apparatus, but yet it is conceivable that not only the photosensitive drum 1d concerned in image formation but the drums 1a to 1c not concerned in image formation are worn by the intermediate transferring belt 6 and the end of the life of the photosensitive drums is hastened.
In such a case, the black cartridge is concerned in image formation and therefore, it has been relatively easy to control the life thereof and it can be precisely reported to the user, but the cartridges of the other colors are not concerned in image formation and therefore, an error has occurred to the time for controlling the life thereof and the end of the life could not be sometimes precisely reported to the user.
Also, there have been cases where when a problem has arisen on the part of the user, the reason therefor cannot be understood well even if an attempt is made to analyze why the problem has arisen.
Further, in the color image forming apparatus of the above-described construction, a system for changing the process speed, like e.g. OHP sheets, and making transmissivity good has been put into practical use.
In such a case, there is no problem if there can be adopted such a construction that only the speed of the fixing apparatus is changed, but the downsizing and lower cost of the apparatus are sought after, whereby the distance between the transferring means and the fixing apparatus cannot be made as long as the size of e.g. OHP sheet and therefore, there has been proposed a system for changing the process speed of the image forming operation itself (the image forming speed).
Again in the color image forming apparatus of such a construction, each constituent portion is designed so as not to affect the life of the photosensitive drums as much as possible, but the influence cannot be completely eliminated, and though slightly, the life of the photosensitive drums is affected, or has been affected by an accident, for example, the use of unexpected OHP sheets or the like.
In such a case, heretofore, an error occurred when the life was controlled and it could not sometimes be precisely reported to the user.
Also, when there arose a problem on the part of the user, there was a case where the reason for the problem could not be understood well even if an attempt was made to analyze it.
The present invention has been made in view of the above-noted problems, and an object thereof is to provide an image forming apparatus which is high in cartridge life control accuracy.
Another object of the present invention is to provide an image forming apparatus comprising:
a plurality of image forming stations for forming an image on a recording material, each of the plurality of image forming stations having a memory; and
writing means for writing data into the memories;
wherein when the image is formed on the recording material without at least one of the image forming stations being used, the writing means writes use data into the memory of the station used and the memory of the station not used.
Still another object of the present invention is to provide a unit mounted on an image forming apparatus on which a first unit and a second unit are mountable, the unit comprising:
a memory;
wherein the memory stores therein the use data when an image is formed by use of at least the first unit, and the use data when an image is formed by use of not the first unit but the second unit.
Yet still another object of the present invention is to provide an image forming apparatus comprising:
an image forming station for forming an image on a recording material, the image forming station having a memory; and
writing means for writing data into the memory;
wherein the image forming station can form an image at at least two kinds of speeds, and the writing means writes use data into the memory for each of the image forming speeds.
Still a further object of the present invention is to provide a unit comprising:
a memory;
wherein the memory stores therein use data for each image forming speed.
Further objects of the present invention will become apparent from the following detailed description when read with reference to the accompanying drawings.